Safety ski bindings have long been a feature of quality ski equipment since they function to release a skier's boot when forces dangerous to the skier are applied thereto. Such forces are commonly experienced, for example, in the case of a fall where the leverage of an attached ski could cause the skier's lower limbs to experience potentially damaging forces. Release of the boot from the binding in such instances minimizes the forces experienced during the fall, thus helping to prevent injuries, including bone trauma to the skier's ankles and legs.
In the past, bindings have typically featured mechanical release mechanisms; however, considerable effort has been devoted to the development of release bindings that rely upon electronic circuitry since bindings incorporating such circuitry offer the possibility of more precise and consistent response to whatever threshold release force is selected to activate the binding release.
One form of such electronic binding comprises electronic circuitry that includes at least one transducer positioned to detect forces acting on the bindings in a particular direction. The transducers produce a release-triggering current when subjected to a threshold force value, resulting in operation of the mechanism and release of the skier's boot. The current, for example, is operative to energize or de-energize an electromagnet, depending upon the circuitry, the components of the mechanism then acting to produce the desired release.
While electronic bindings have much to commend them, they have the disadvantage of being susceptible to inoperativeness caused by the occasional failure of a component in the circuit, the electromagnet, or in the battery energizing it. Such failures are sometimes difficult to detect beforehand, and so can result in failure of the binding to release when necessary with the injurious consequences which that can entail.
In view of the potential advantages that electronic bindings offer, a number of efforts have been made to overcome the drawbacks described, and remedial designs have been utilized to compensate for such drawbacks.
German Patent No. 2,737,535 A-1, for instance, employs shear pins to support the sole holder portion of the binding. When the binding is subjected to unacceptable stresses, the shear pins fail, releasing the sole holder and freeing the boot from the ski binding. Unfortunately, the holder thus released must be re-attached to the ski, an operation not readily performed on a ski slope. Consequently, the necessity of reattachment can seriously interrupt skiing activity for the day on which the accident occurs, interfering with the pleasure of skiing.
Another approach to the problem is that envisioned by German Patent No. 2,938,756 A-1 which employs an electronic logic system that depends upon electronic monitoring of the release system'state of operativeness. The device incorporates switching means that shifts the release function from one activated by electronics to a mechanical release system when a fault develops. The drawback of such an approach, however, is that additional circuitry is required, an expedient that is both expensive and also vulnerable to malfunctioning.
German Patent No. 3,017,841 C-2 provides dual release functionality including both mechanical and electronic release mechanisms. In this device also, however, it is necessary that an error be detected and a signal generated for subsequent transmission to an operating mode switch capable of changing the release system from an electronic to a mechanical release mode.